The present invention relates to a feed apparatus for a printing press, which chucks sheets stacked on a pile board one by one from the uppermost one and feeds the chucked sheet.
As shown in Japanese Utility Model Laid-Open No. 3-24511, a conventional feed apparatus for a printing press comprises the first sucker member which chucks sheets which are supported to be vertically movable and stacked on a pile board one by one from the uppermost one, and the second sucker member which chucks the sheet transferred from the first sucker member and conveys it. Of the two sucker members, the first sucker member comprises a cylindrical guide nozzle, a sucker fitted on the outer surface of the guide nozzle to be vertically movable and having a chuck hole in its lower end face, and a sucker spring which is elastically mounted between the sucker and guide nozzle and biases the sucker downward with respect to the guide nozzle.
In this arrangement, when the first sucker member that has moved downward is moved close to the sheet and air in the guide nozzle is drawn, the sheet is chucked by the chuck hole of the sucker. When the sheet closes the chuck hole, the interior of the sucker is set in a negative pressure state, and the sucker moves upward against the spring force of the sucker spring. Subsequently, when the sheet is chucked by the second sucker member, it is transferred to the second sucker member. After that, air drawing into the guide nozzle is stopped, and the second sucker member conveys the sheet.
In the conventional feed apparatus for the printing press, when the second sucker member chucks the sheet and conveys it, drawing air supply to the guide nozzle of the first sucker member is stopped. Thus, the spring force of the sucker spring moves the sucker downward. At this time point, since the second sucker member has not completely conveyed the sheet yet, the sheet is present below the sucker of the first sucker member. Therefore, the sucker of the first sucker member that moves downward may come into contact with the sheet. This may scratch the sheet, or separate the chucked sheet from the second sucker member.
When the sucker of the first sucker member pushes the sheet downward, the sheet may interfere with blowing air discharged from a leveling foot. In this case, air discharged from the leveling foot is not supplied to the portion between the first and second sheets, and the sheets cannot be reliably fed one by one.